Process of manufacturing artificial compositions



Sept. 27, 1938. 5, TEN CATE 2,131,022

PROCESS OF MANUFACTURING ARTIFICIAL COMPOSITIONS Original Filed May 16,1934 ve/vEar Patented Sept. 27, 1938 UNITED STATES PROCESS orMANUFACTURING an'rniomr.

' COMPOSITIONS Steven Jan Blaupot ten Cate, Kootwijk,

Netherlands Application May 16, 1934, Serial No. 726,001 Renewed January8, 1937.

In Germany May 20,

4 Claims. ((31. 91--68) It has been proposed to manufacture artificialcompositions by impregnating loose fibrous ma- .terials, card fleeces,felt fieeces,'etc., with binding agents. In manufacturing processes ofthis 5 character various difliculties occur and the products obtainedgenerally do not have the mechanical properties desired for certainpurposes, 'e. g. for leather substitutes. In most cases impregnation isefiected by immerging the fibrous material in a bath of the impregnatingliquid and subsequently passing the impregnated material to the pressingcylinders used for removing the excess of the impregnating liquid. Oneof the drawbacks of this process is that the fibres of the materialimpregnated with the liquid binding agent often adhere to the cylindersused for expressing the liquid. I

i It has further been proposed to pour the binding agent on the materialsupplied by a conveyor 120 belt, or to mix the fibres and the bindingagent uniformly in a mixing device, to dry the mixture and to press thesame if desired.

' According to other priorprocesses the fibrous material is felted so asto obtain a certain coherence between the fibres, in order to preventthe same from adhering to the cylinders. In this case, however,impregnation is not so satisfactory because the impregnating liquid doesnot penetrate in the felted material as easily as in the loose fibrousmass.

, In some of the'prior processes the material is impregnated, e. g. withlatex, to such an extent, that the final product contains a largeproportion of the binding agent,'e. g. -50% rubber.

The invention relates to a process of manufacturing artificial materialscontaining 38-60%' of the binding agent from a loose cohering body offibres and a dispersion or solution of the binding agent, which ischaracterized by the feature that the fibrous material is impregnatedtwo or more times by means of cylinders, and that the impregnatedfibrous material is dried and calendered between the subsequentimpregnation steps.

In order to obtain a final product with the 5 desired mechanicalproperties, especially for manufacturing artificial leather of excellentquality from fibres and a rubber dispersion or solution, it is essentialthat the proportion of the binding agent is between the limits mentioned5Q above. If the, final product contains less than 38% of rubber it hassubstantially the character of a fibrous material, whereas productsconsisting of more than 60% of rubber have rubberlike properties. Incontradistinction therewith products obtained according to theinvenfelted fibrous material tion and containing from 3 8 60% of rubberhave the characteristical properties of genuine leather.

As starting materials fibres in the form of a loose fleece are used, e.g. a card fieece, a fleece of paper wedding or a very loose,insuificiently produced by means of a felting willow. v

Suitable binding agents'are rubber-dispersions or solutions, e. g. latexand rubber emulsions obtained from latex, or the well-known rubbersolutions in volatile solvents, and the invention will be describedbelow with a view to manufacturing artificial leather from fibrousmaterials and rubber dispersions and solutions of this character.However, other binding agents, e. g. tar-like substances, orsodiumsilicate, may also be used. The artificial compositions obtainedaccording to the last mentioned process are e. g. suitable to be used aspacking materials and the invention also covers processes ofmanufacturing products of this character.

With the expression impregnating by means of cylinders" I understand aprocess in which the fibrous material is passed through cylindersbetween which a certain volume of liquid is maintained or supplied. Ihave found that this process has substantial advantages as compared withthe well-known impregnating methods in which the fibrous material ispreviously saturated with the liquid, e. g. by immerging the fibrousmaterial in alatex bath and subsequently passing the materialimpregnated in this way to the cylinders where the excess of liquid isexpressed, the coherence of the loose fibrous material being oftenseriously injured as a result of the pressing operation. 4

In the process according-to the invention the rate with which thefibrous material is passed through the pressing device and the height ofthe body of liquid between the cylinders or the rate of supply of thesaid liquid can be easily controlledso as to allow fibrous material of apredetermined absorption power to be impregnated to the centre, just atthe point where the impregnated product leaves the cylinder. In case thefleece is not yet fullyimpregnated in this stage a non-homogeneousproduct is obtained, as the inner layers -do not contain a sufficientamount of the binding agent.

If on the contrary the fibrous material is allowed to become thoroughlysaturated with liquid before being pressed between thecylinders, theabove mentioned drawback connected with the prior impregnation processesarises.

Preferably smooth cylinders rotating with equal side elevation of anapparatus suitable for carrying out the invention.

After being impregnated the product is dried; the water or the solventis evaporated and I obtain a porous sponge-like mass consisting offibres each of which is covered with a thin coating of rubber. The firstimpregnation has the primary object to consolidate the fibrous materialso as to form a coherent mass and therefore the rubber dispersion orsolution usedcontains no fillers or only a small amount of fillers.ever, advantageous to admix the liquid used for the first impregnationwith substances improving the strength and the stiifness of the rubber.

The dried mass is now passed between calenders, the fibres thereby beingpressed together to form a strongly cohering'mass, owing to thewellknown property of 'unvulcanized rubber layers of being easily unitedbysimple pressing. This intermediate calendering step between the firstand the second impregnation and drying is of essential importance forobtainingthe desired mechanical properties of the final product.

After being calendered the material has already leather-like proper-tiesto a certain extent. Mi-

croscopical examination of the material, however,

shows that it' has a very porous structure and that it contains a largenumber of cavities, formed by the evaporation of the water of thesolvent intro-- ,ce ntrated rubber dispersion, containing at the sametime a substantial amount of fillers;

After the second impregnation the material is dried again. The productcontaining a certain amount of newly formed cavitie s is again stronglypressed between calendars so as to produce a compact material with averylow elasticity.

Usually two impregnations are sufficient to obtain satisfactory results.In some cases; ,viz. when a product of exceedingly low porosity isrequired, it is advantageous to repeat th impreghating, .drying andcalendering process in'order to fill up the cavities still existingafterthe second stage.

In. order to obtainin each impregnating step the proportion of bindingagent desired, the distance between the cylinders is controlled so as tomaintain a predetermined, relatively large part of the impregnatingliquid in the fibrous material.- It is therefore necessary to use arather low pressure of the pressing 1 cylinders. In this case, however,the fibres have a strong tendency to adhereto the cylinders, so thatserious difllculties occur during the impregnating process and the 5brous surface.

It is, howtaken, however, that the impregnating process is not impededby this treatment, and it is therefore necessary that the surface of thefleece remains sufliciently open. For this purpose the adhesive ispreferablyxsprayed or atomized on the fibrous 5 material. A verysuitable adhesive for this preliminary treatment is'rubber in the formof a dilute dispersion or solution. Other adhesives, however, i may alsobe used, e. g, starch'products, glue, cellulose derivatives and thelike. The amount of adhesive used for this preliminary treatment isgenerally very low.

When usingflbres such as sisal, jute, hemp and coco fibres, I have foundthat a better adhesion between the fibres and the binding agent isobtained by opening? the elementary fibres before manufacturing, thefleece. To this purpose the fibres can be subjected to a preliminarytreatment by boiling the same with an aqueous liquid, e. g. with causticsoda. The tlme'andthe temperature of boiling are selected so as toobtain a material in which the outer layer of the fibres is more or lessdestroyed and a part of the olementary fibres is free. A completedestruction of the outer layer, however, must be avoided as this resultsin a marked reduction of the tensile strength.

Boiling the fibrous material with caustic soda further has a greatadvantage, also when using cotton, in that the impregnation speed issubstantially increased. v A high impregnation speed, however, is veryimportant for the impregnating process by means of cylinders accordingto the invention, as in this case only a fraction of a second isavailable for the impregnation.

In the third place the elasticity of the final product is materiallydecreased when using fibrous materials pretreated by the above mentionedboiling process- As stated above, a low elasticity is a very valuableproperty for leather substitutes.

If. the artificial leather obtained according to the invention iscovered with a lacquer coating, this coating can be provided after thesecond impregnation previous to calendaring. This method has theadvantage that the lacquer partly penetrates into the cavities formedduring the second drying step so that the lacquer. coating is firmlyunited with the material. In this case a grain calender is used whichallows various patterns to be impressed in the mass.

The product according, to the invention has substantial advantages forig is purpose as compared with the well-known leather substitutesobtained by impregnating fabrics as a deeper relief is produced.

For manufacturing rubber compositions I preferably use aself-vulcanizing rubber dispersion or solution; the chemical reaction isinitiated by 6 drying the lacquer coating or by impressing the grain ,atelevated temperatures; the reaction proceeds when maintaining theproduct at temperatures between 30and C. In this way the grain isimpressed in the unvulcanized material and is made permanent byvulcanizing.

In the drawing the loose coherent fiber fleece in the form of an endlessband I is co nducted to the conveyorbelt 2 on which the upper side ofthe fleece is lightly sprayed with latex by means The fleeceis driedagain and conducted by means of the conveyor belt I to the impregnatingapparatus consisting of two cylinders 8 which rotate at the same speed.Latex is supplied between the cylinders from the container 9 and therate of supply is controlled so as to maintain a body of latex of thedesired height between the cylinders. v

The impregnated fleece I is passed through the drying chamber I2 bymeans of rods II on which the fleece is dried in freely suspendedcondition. The dry product is conducted to the device I3 in which theirregular side portions I4 are out ofi by means of knives. The fleece isnow compressed between the calenders I5 the pressure of which can becontrolled and then wound up into the roll I6.

The last part of the process, that is impregnation-drying-calendering,is preferably repeated one or more times.

I claim:

1. A process of manufacturing artificial leather containing 38% to 60%of rubber by impregnating a loosely coherent fiber fleece with a rubberdispersion, comprising treating the surface of the fiber fleece prior toimpregnation with a small amount of an adhesive so as to make the fibersof the surface stick together without substantially reducing thepermeability of the surface for the impregnating agent, and subsequentlyimpregnating the material in a plurality of impregnation steps bypassing the same between low pressure cylinders between which a body ofrubber dispersion is maintained, drying and calendering the materialafter each impregnation step and vulcanizing the rubber.

2. A process of manufacturing artificial leather containing 38% to 60%of rubber by impregnating a loosely coherent fiber fleece with a rubberdispersion, comprising treating the surface of the fiber fleece prior toimpregnation with a small amount of an adhesive so as to make the fibersof the surface stick together without substantially reducing thepermeability of the surface for the impregnating agent, and subsequentlyimpregnating the material in a plurality of impregnation steps bypassing the same between low pressure cylinders between which a body ofrubber dispersion is maintained, drying and calendering the materialafter each impregnation step, and vulcanizing the rubber, the firstimpregnation step being carried out with a rubber dispersion which doesnot contain an appreciable amount of fillers and the furtherimpregnation steps being carried out with rubber dispersions containinga large amount of fillers.

3. A process of manufacturing artificial leather containing 38% to 60%of rubber by impregnating a loosely coherent fiber fleece with a rubberdispersion comprising boiling the fibrous material with an aqueousliquid, drying the same, treating the surface of the fiber fleece priorto impregnating with a small amount of an adhesive so as to make thefibers of the surface stick together without substantially reducing thepermeability of the surface for the impregnating agent, subsequentlyimpregnating the material in a plurality of impregnation steps bypassing the same between low pressure cylinders between which a body ofrubber dispersion is maintained, drying and calendering the materialafter each impregnation step and vulcanizing the rubber.

4. A process of manufacturing artificial leather containing 38% to 60%of rubber by impregnating a loosely coherent fiber fleece with a rubberdispersion comprising boiling the fibrous material with a caustic sodasolution, drying the same, treating the surface of the fiber fleeceprior to impregnating with a small amount of an adhesive so as to makethe fibers of the surface stick together without substantially reducingthe permeability of the surface for the impregnating agent, subsequentlyimpregnating the material in a plurality of impregnation steps bypassing the. same between low pressure cylinders between which a body ofrubber dispersion is maintained, drying and calendering the materialafter each impregnation step and vulcanizing the rubber.

STEVENJAN BLAUPOT TEN CA'I'E.

